Static magnetic devices such as transformers and inductors are essential elements in circuits requiting energy storage and conversion, impedance matching, filtering, EMI suppression, voltage and current transformation, and in resonant circuits. These devices, as now constructed, tend to be bulky, heavy and expensive as compared to the other components of the circuit. Their cost tends to be dominated by construction costs since manual operations still form a part of the production process for many of these components.
No widely used method of constructing and fabricating magnetic components has resulted in any radically new and different magnetic component structure. The current methods of manufacturing magnetic components have not changed significantly from the traditional methods involving the mechanical process of wrapping a copper wire around a magnetic core material or around an insulating former (i.e. bobbin) containing core material. Hence, despite the trend towards low profiles and and miniaturization in other electronic components, and the trend to integration and other circuit packaging techniques, the magnetic components in current use generally retain traditional constructions.
Recent approaches to changing the construction of magnetic components have included layered or drop-in windings as opposed to wound windings such as disclosed in U.S. Pat. No. 4,583,068. These techniques have introduced new mechanical construction methods to significantly reduce hand operations and construction costs.
Another recent approach to magnetic component design is a multilayer chip inductor using thick film technology and designed as a surface mount component. This approach is disclosed in an article entitled "Recent Topics in Soft Ferrites" by K. Okutani et al presented at The Int Conf. on Ferrites, ICF 5, January (1989). The magnetic component designated, a "chip type" inductor or transformer, is constructed by a sequence of thick film screen print operations to build up layers on an individual layer by layer basis, which are then fused by co-firing. This process, which uses printed layers of ferrite paste and conductor paste (for the windings) is limited to the use of a single material as both the magnetic and insulating material. This use of a single material limits the choice of materials to those having a relatively high resistivity such as CuNiZn ferrite material which, however, has which, however, has a low permeability and low breakdown voltage capability. The process is also limited to certain geometries. Additionally, because of the absence of suitable non-magnetic inclusions in the construction process, the net magnetic flux produced by the electrical excitation of the winding is not fully coupled to each turn of the winding. In the transformer case, this leads to a leakage inductance capability inferior to that of transformers made by traditional construction techniques.